"""Canonical serializer + INV-12 round-trip lock (SD-0002 §6.5.5, §6.8)."""
import csv
import io

from app.domains.products import serialize
from app.domains.products.diff import CatalogImage, CatalogProduct, CatalogVariant


def _product(**kw) -> CatalogProduct:
    """A minimal no-option catalog product (one all-NULL variant)."""
    base = dict(
        id=1, handle="moon-mug", title="Moon Mug",
        option_names=(None, None, None),
        fields={
            "title": "Moon Mug", "description_html": None, "vendor": "Acme",
            "product_type": "standalone", "google_product_category": None,
            "tags": [], "status": "active", "published": True,
        },
        variants=[CatalogVariant(
            id=1, options=(None, None, None), position=1,
            fields={"sku": "WG-MUG", "barcode": None, "price": None, "cost": None,
                    "weight": None, "weight_unit": None, "volume": None,
                    "volume_unit": None, "tax_id_1": None, "tax_id_2": None,
                    "inventory_tracker": None, "inventory_qty": None,
                    "variant_image": None})],
        images=[],
    )
    base.update(kw)
    return CatalogProduct(**base)


def _rows(products) -> list[dict]:
    text = "".join(serialize.catalog_to_csv(products))
    return list(csv.DictReader(io.StringIO(text)))


def test_header_is_full_canonical_set():
    text = "".join(serialize.catalog_to_csv([_product()]))
    header = next(csv.reader(io.StringIO(text)))
    # Handle + Title first; every known column present exactly once.
    assert header[0] == "Handle"
    assert "Title" in header and "Variant SKU" in header and "Image Src" in header
    assert len(header) == len(set(header))


def test_single_no_option_product_one_row():
    rows = _rows([_product()])
    assert len(rows) == 1
    assert rows[0]["Handle"] == "moon-mug"
    assert rows[0]["Title"] == "Moon Mug"
    assert rows[0]["Variant SKU"] == "WG-MUG"
    # A no-option product emits no option values.
    assert rows[0]["Option1 Value"] == ""


def _star_tee() -> CatalogProduct:
    """A 3-variant, 2-image product (the sample.csv shape)."""
    return CatalogProduct(
        id=2, handle="star-tee", title="Star Tee",
        option_names=("Size", "Color", None),
        fields={"title": "Star Tee", "description_html": None, "vendor": "Acme",
                "product_type": "standalone", "google_product_category": None,
                "tags": ["apparel", "tees"], "status": "active", "published": True},
        variants=[
            CatalogVariant(id=10, options=("S", "Indigo", None), position=1,
                           fields={"sku": "WG-TEE-S", "variant_image": None}),
            CatalogVariant(id=11, options=("M", "Indigo", None), position=2,
                           fields={"sku": "WG-TEE-M", "variant_image": None}),
            CatalogVariant(id=12, options=("L", "Indigo", None), position=3,
                           fields={"sku": "WG-TEE-L", "variant_image": None}),
        ],
        images=[
            CatalogImage(id=1, source_url="https://x/a.jpg", position=1, alt_text="front"),
            CatalogImage(id=2, source_url="https://x/b.jpg", position=2, alt_text="back"),
        ],
    )


def test_multivariant_with_images_interleaves():
    rows = _rows([_star_tee()])
    assert len(rows) == 3  # max(3 variants, 2 images)
    # Product-level fields only on the first row.
    assert rows[0]["Title"] == "Star Tee" and rows[1]["Title"] == ""
    assert rows[0]["Tags"] == "apparel, tees" and rows[1]["Tags"] == ""
    # Option names on row 0; option values on every variant row.
    assert rows[0]["Option1 Name"] == "Size" and rows[1]["Option1 Name"] == ""
    assert [r["Option1 Value"] for r in rows] == ["S", "M", "L"]
    assert [r["Variant SKU"] for r in rows] == ["WG-TEE-S", "WG-TEE-M", "WG-TEE-L"]
    # Two images on the first two rows; third row has no image.
    assert [r["Image Src"] for r in rows] == ["https://x/a.jpg", "https://x/b.jpg", ""]
    assert [r["Image Position"] for r in rows] == ["1", "2", ""]


def test_more_images_than_variants_emits_image_only_rows():
    p = _product(images=[
        CatalogImage(id=1, source_url="https://x/a.jpg", position=1, alt_text=None),
        CatalogImage(id=2, source_url="https://x/b.jpg", position=2, alt_text=None),
        CatalogImage(id=3, source_url="https://x/c.jpg", position=3, alt_text=None),
    ])
    rows = _rows([p])
    assert len(rows) == 3  # 1 variant, 3 images
    assert rows[0]["Variant SKU"] == "WG-MUG"
    assert rows[1]["Variant SKU"] == "" and rows[1]["Handle"] == "moon-mug"
    assert [r["Image Src"] for r in rows] == ["https://x/a.jpg", "https://x/b.jpg", "https://x/c.jpg"]